Synthesis of dodecyl mercaptan using high energy radiation

ABSTRACT

A process is disclosed for the synthesis of dodecyl mercaptan from a 50:50 mixture of dodecene and hydrogen sulphide at a temperature in the range 0* - 50* C. and a pressure of about 20 atmospheres, using cobalt-60 radiation to effect the reaction. A full flow sheet is described.

I United States Patent [1 1 3,661,745 Hills et al. 1 May 9, 1972 1 SYNTHESIS OF DODECYL 51 Int. Cl. ..B01j 1 MERCAPTAN USING HIGH ENERGY [58] Field of Search ..204/l62 RADIATION [56] References Cited [72] Inventors: Peter Robert Hills, Abingdon; Michael William Spindler, Cowley; Kenneth Wal- UNITED STATES PATENTS .M t igf acauly Dldco an of En 3,223,738 12/1965 Crain et al. ..204/l62 3,257,302 6/l966 Warner ..204/162 [73] Assignee: United Kingdom Atomic Energy Authority,

London England Primary Examiner-Benjamin R. Padgett [22] Filed; Sept 9 Attorney-Larson, Taylor and Hinds A process is disclosed for the synthesis of dodecyl mercaptan [30] Forelg Apphcamm Pnomy Dam from a :50 mixture of dodecene and hydrogen sulphide at a Se t. 29, 1967 Great Britain ..44,602/67 temperature n the range 0 50 C. and a pressure of about 20 atmospheres, using cobaltradiation to effect the reaction. [52] US. Cl ..204/ 162 HE A full flow sheet is described.

2 Claims, 1 Drawing Figure SYNTHESIS OF DODECYL MERCAPIAN USING HIGH ENERGY RADIATION BACKGROUND OF THE INVENTION This invention relates to the synthesis of docecyl mercaptan 5 React working P F P 20 atmospheres? Reaction by the use f radiation perature 20 C. Provision must be made to keep this tem- In the radiation synthesis of dodecyl mercaptan the main f below lfbollmg 15 P to reaction 111. That the reactor geometry IS a cylinder containing a cencu H H2 C12 H25 SH trally located tube in which a cobalt-60 radiation source and a side reaction is:

2 H24 H2 5 (Cl2 H292 5 Safety and control devices are not shown but it may be necessary to provide a dump tank for the reactor. SUMMARY OF THE lNVENTlON The flow sheet shows the compressor (a) from Column Ill The invention provides a process for the radiation synthesis recycling hydrogen Sulphlde mm the i Guam Smce this column operates under vacuum some arr mleakage may occur, of dodecyl mercaptan, wherein a 50.50 mixture of dodecene this may lead to a requirement to discharge the hydrogen suland hydrogen sulphide is caused to react at a temperature hide from (a) that than rec clin it and/or to wide 8 within the range 050 C. and at a pressure of about atp y g p vent with a blow-ofi' valve and cold trap to atmosphere, for mospheres.

non-condenstbles arriving at the condenser which also pro- BRIEF DESCRIPTION OF THE DRAWING 2O vides a control of the high pressure end of the plant.

t Conversion proceeds to a virtually asymptotic value, whose TheFCCOmPaHYIWdTaWmg1S aflow dlagramlnusn'atmg the level increases with decreasing proportion of olefine in the mvemlon' reaction mixture. Reaction rates in general decrease markedly above the 50-60 percent conversion level. However using a DESCRIPTION OF THE PREFERRED EMBODIMENT larger reactor giving more efiicient use of cobalt, it may be The flow diagram of the accompanying drawing is based on desirable to react to 70-80 percent conversion (so reducing a 75 percent conversion of dodecene in a 50:50 mixture with recycle). hydrogen sulphide. In the drawing FIGS. 1-9 represent heat in spite of the decrease in percentage conversion (per unit exchangers, capable of controlling the temperature of reactime) asthe dodecene proportion increases, the mass yield for tants and reaction products at various points in the plant, a given volume of reaction mixture increases. Thus it is best to FIGS. a-d represent pumps/compressors and FIGS. l-lll operate at the stoichiometric ratio (50 m-percent) in the feed, represent columns for the separation of unreacted material as shown in the flow sheet. from the reaction product. When considering possible variants in the process parame- The reaction is carried out at about 20 atmospheres presters it is important to consider the nature of the liquid flows in sure and at a temperature in the range 0- 50 C. Under these the reactor, and also the dimensions of the reactor required to conditions the side reaction above described accounts for 3-4 deal with these flows. Thus assuming that the liquids in the percent of the dodecene conversion. reactor are in plug flow at 20 C., and receive 5 X l0 R/hr. in Heat exchanger heating and cooling loads, and-pump/coman outer zone, 5 X 10 R/hr. in an inner zone of the reactor pressor requirements are as follows: then according to the following table:

Reaction Time for mixture Reactor reaction feed rate volume Example (mins.) (l/hr.) (litres) Recycle flow sheet 1. m. percent CIZHQ; to convn. +130=250 77 320 As shown in accompanying drawing. 2. 50 m. percent CIQHZ; to 50% conv'n.... 40+30=70 115 Flow sheet similar to above, but with recycles increased 4-fold. 3. 20 m. percent C12H21 to 80% convn... 80+70=150 100 250 Large proportion of H28 requires extra column before I, to flash and condense some 1,600 moles/hr. (55 kgJhr. H28 at 20 atms. Subsequent layout and news as example (1).

H Exchanger 92 K Cal/hf- H r 50 if plug flow'cannot be achieved and a mixed reactor is used, ea mg reaction takes place at virtually the discharge composition. I so 7 3500 This would decrease conversion to 60-65 percent and require 2 2500 8 100 a recycle increase over that shown in the flow diagram. in ad- 3 200: 9 2500 dition, allowance should be made for increased recycle to 55 compensate for decrease of conversion and/or required in- 6 2700 crease in output from the reactors. Reaction rates being in- Pumps/Compressors creased at temperatures above 20 C., which are likely in the reactor. y wats At an overall G value of 2 X 10, the calculated cobalt a/ IOmm-760mm 500 (1.5 l/min) 60 requirement is 2250/ cunes where n is the absorption efi'tb/ 1 atm-Satm 200 ciency in the liquid reactants. This G value corresponds to 75 mm %88 percent conversion of a 50m percent mixture, at a level of 5 X 16 I l0 R/hr. If 11 0.5,source required 5,000 curies. The separation columns {-111 comprise flash columns 1 and Now a 60 cm. long source of 5,000 curies will give the dose 11 at 5 and l atmospheres respectively and a vacuum distilla- 5 rate of 5 X 10 R/hr. In a 10 cm. annulus at a mean radius of 20 tion column ill at ca. 10 mm. mercury. All the columns cm. from the source center, i.e. the radiation level checks for operate at C. reboiler temperature and a condensate the reactor geometry, which is a cylinder with a central tube to temperature of 40 C. hold the source. The required reactor volume is then some Flow rates of reactants and products at points l0-20 in the 300 liters if plug flow can be achieved. For a reactor l ft. I.D. drawing, expressed as Kgms per hour are as follows: 70 X 2.5 ft CD. the volume 117 liters/ft. length. Hence a reactor about 3 ft. long X 2.5 ft. O.D. is adequate.

However this assumes plug flow of reactants which will be difficult at these low flows. Stagnant regions and bypassing of reactants are possible. An alternative is a fully mixed reactor giving a decreased conversion requiring increased recycle. The reactor D. is then increased to 3 ft., and a conversion level of around 60-65 percent of dodecene allowed for by increased recycle. Thus reactor volume is not increased excessively because the outer levels of radiation assumed for the plug flow case (example 3) are below those likely for the ac-' tual source and geometry. A further alternative form of reactor is a stirred reactor. discharging via a coil wound round the central tube, to give a high final irradiated level and improved conversion.

We claim:

1. A process for the radiation synthesis of dodecyl mercaptan comprising passing an equimolar mixture of dodecene and hydrogen sulphide through a reactor vessel, simultaneously irradiating the mixture in the reactor vessel with high energy ionizing radiation, the reaction temperature being maintained in the range 0-50 C and the reaction pressure being about 20 atmospheres.

2. A process according to claim 1, wherein the reaction temperature is maintained at 20 C. 

2. A process according to claim 1, wherein the reaction temperature is maintained at 20* C. 